Normally, an automatic developing machine is used to develop many exposed PS plates.
In order to develop many exposed PS plates, the following two methods have been adopted. One is to spray a developer on PS plates while they are transferred in a horizontal direction. The other is to immerse PS plates by bending them in a developing tank which contains a large quantity of a developer while they are transferred. In these methods, it is necessary to prepare large quantities of a developer in developing one PS plate. A developer is recycled in these methods. As a result, the developer is deteriorated due to repeated developments of PS plates as well as absorption of carbon dioxide, which necessitates the deteriorated developer to be replaced, and as such, makes a developing operation very troublesome.
In order to solve the disadvantage caused by the above-described method, methods of stably developing PS plates by recycling a large quantity of a developer have been developed in the art. In these methods, a replenisher is supplied to prevent a developer from being deteriorated. These methods are disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) Nos. 144502/1975, 115039/1980, and 95349/1983. In these methods, though the frequency of a developer exchange is reduced, it is still necessary to exchange a developer. Further, a replenisher is not necessarily supplied with required accuracy. In addition, it is very troublesome to adjust the amount of a replenisher according to the dimension of the PS plates to be developed. Furthermore, it is necessary to provide a replenishing device which is expensive and care must be taken so that the replenishing device may work in a good condition.
An apparatus intended to eliminate the need for supplying a replenisher and reduce the amount of a developer to be used was disclosed in Japanese Patent O.P.I. Publication No. 32044/1980. The apparatus is provided with a developer diffusion plate adjacent to a PS plate-transfer path mounted in an automatic developing machine whereby a developer applied to a PS plate spreads entirely over the PS plate. According to this method of developing PS plates using a small amount of a developer, an uneven development occurs unless a relatively large amount (300-500 ml/m.sup.2) of a developer is supplied. Even if a relatively large amount of a developer is supplied, residual film of 0.5 mm in width are formed at the top portion and side edge portions of the PS plates.
It is therefore an object of the present invention to provide a method of developing PS plates whereby the top and side edge portions of the PS plates are reliably developed using a small amount of a developer and a developing apparatus which performs this developing method.